Abstract:Climate change intensification has made drought a major threat to food security of China. To safeguard food security and ensure sustainable development of agriculture, it is imperative to conduct in-depth research on drought exposure risks to croplands of China. Traditional drought assessment methods may systematically overestimate future drought risk due to neglect of the dynamic regulatory effects of CO2 (SPEI(CO2)) on stomatal conductance of vegetation. An improved standardized precipitation evapotranspiration index incorporating physiological effects of CO2 was integrated with multi-model data of CMIP6. Using the Sen slope estimator, Mann-Kendall test, an exposure assessment model, and an additive decomposition method considering both climate and land use factors, drought trends, cropland exposure, and driving contributions were systematically quantified across nine major agricultural regions of China during the historical period (1961—2022) and future scenarios (SSP1-2.6, SSP2-4.5, and SSP5-8.5). Results showed that during 1961—2022, grids exhibiting an increasing trend of drought accounted for 77% and 64% for SPEI and SPEI(CO2), respectively. For the future period (2023—2100), SPEI indicated a weak trend of drought intensification (Sen slope: -0.0013a-1), while SPEI (CO2) suggested a weak trend of humidification (Sen slope: 0.0011a-1), with the most significant differences observed in the northern arid and semiarid region (NASR) and Qinghai-Tibet Plateau (QTP). By the end of the 21st century, the national average cropland exposure (based on 0.25° grids) under SSP5-8.5 was estimated at 57km2/a for SPEI and 10km2/a for SPEI (CO2), with NASR showing the most significant reduction in peak exposure. Attribution analysis revealed that climate change dominated dynamics of future cropland exposure: increased precipitation in the near term (2021—2040) and mid-term (2041—2060) reduced risk of exposure, whereas rising temperatures in the long term (2081—2100) amplified exposure. The effect of CO2 suppressed evapotranspiration and reversed intensification of drought in major agricultural regions under SSP2-4.5 and SSP5-8.5 scenarios during 2081—2100.
